vents and drain for heat exchangers 5

[myck]

I would like to seek help regarding requirement for vent and drain for heat exchangers. Kindly advise when this is necessary if the process data sheet did not show this nozzles on their documents.

 

[SnTMan]

myck, all chambers should be capable of being vented & drained independent of process piping. Sometimes necessary to have separate vent & drains just for hydro, depending on vessel orientation.

You have to look at your design and insure that it can be vented / drained.

Regards,

Mike

 

[gr2vessels]

My two cents;- if it is a plate heat exchanger, the drain and vent are not included on the datasheet.
Cheers,
gr2vessels

 

[strain2]

In first place, such requirements have to be spelled out in Process Data Sheets.

As "SnTMan" mentioned, all exchangers shall be capable of venting and draining for hydrotest purposes. If such can be achieved with other nozzles, nothing wrong with this. Again oreintation of such nozzles (vent to be at the highest point and drain to be at lowest point) during hydrotest is vry important. Other methods can also be used if nozzle used for venting purpose is not at the highest point.

Just my thoughts..

Strain2

 

[gr2vessels]

myck, is this a shell and tube heat exchanger or other type?

 

[BigTank]

RE: shell & tube stuff, I'm with strain2. The only time I would consider adding connections of any sort that weren't spec'ed on the process data sheet is if the working fluids were such that cracking loose a process connection to drain the unit would be a bad idea, i.e. caustic fluid, as the collection of the draining fluid is uncontrollable. If the fluid is water or inert gas, I would think all is good to use process connections as vents/drains. This might not be the most 'professional' or 'industry accepted' of philosophies, but in today's marketplace, I'm not going to add cost anywhere it isn't expressly dictated.

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Fitter, happier, more productive

 

[SnTMan]

I *wish* for two things from the customer: 1) Accurate statements of his needs, 2) Serious drawing reviews. Rarely get either these days...

Regards,

Mike

 

[BigTank]

SnT, you in America? Just curious...

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Fitter, happier, more productive

 

[SnTMan]

Nah, Oklahoma

 

[myck]

Hello, How about for BEM/BXM type HE with multi pass?Should we require the vendor to provide vents and drains at th rear side of the HE. I think some of your suggestion would be applicable for BEU type exchanger.

 

[Duwe6]

Free-flowing drain - flush on ID and with a generous radius - is required for shell maintenance. However, if you don't ask for it, you won't get it. Thus "I *wish* for two things from the customer: 1) Accurate statements of his needs, 2) Serious drawing reviews. Rarely get either these days... "

I've got a couple of Hx's that are made from slices of 12 to 18NPS pipe, but were spec'd by our ChemE's at low pressures, low temperatures, and without Full Vacuum. So if I need to use a c/s Hx above it's 300°F MAWP, we have to pay for an Alteration. If the idiot had asked for the "best temperature" he would've found out that the material doesn't derate until 600°F, but no, specify 300 and only get 300. Same for F/V - if he had asked for it, the Hx would've been rated at F/V - small Hx's inherently withstand F/V with no design changes. And our drain nozzle is set-in, and will require significant grinding to get it down to Free Draining.

If you're not experienced enough to see these problems, get somebody who is to help review the proposed dwg's.

 

[SnTMan]

myck, return channels, back channels, shell covers, etc often need their own vents/drains. Examples: Type S shell cover is larger than main shell, will not V&D completely. Return/back channels with less than full tubefield will not V&D completely thru the bundle. And so forth.

Regards,

Mike

 

[Ripz]

As SnT man said "all chambers should be capable of being vented & drained independent of process piping. Sometimes necessary to have separate vent & drains just for hydro, depending on vessel orientation."

For horizontal exchangers, process connections can be used as vents and drains.

For vertical exchanges, there's usually a few centimetres between a tubesheet and a process nozzle which poses a problem to drain and vent. To get over this hurdle, the tubesheets are usually drilled vertically through half the thickness and then then drilled horizontally to atmosphere and connected to a nipple and valve for venting/drainage.

 

[SnTMan]

Yup.